Multi-density Ortholite is a super light weight open-cell technology. The top layer of recovery foam conforms to the foot creating a custom fit every time and provides providing maximum cushioning comfort. The core layer has high rebound absorption which minimizes the harmful impacts form running and quick movements. The contoured support in the heel and arch mimics the foot's natural form and assists proper movement. Ortholite Foam compresses less than 5 percent over time so the cushioning and fit never change. Its anti-microbial formula permeates the entitre product thru and thru against fungus and odor. And it's even machine washable!